The present invention is related to a circular accelerator having a round orbit of charged particles (called closed orbit hereinafter), especially the circular accelerator which is able to store a large electric current, a charged particles injection method thereof, and an apparatus for the charged particles injection method thereof.
Currently, a small size circular accelerator is being used for exposure of semiconductor patterns and applications in the medical field, and so on. In the conventional small size circular accelerator, the charged particles are injected by a multi-turn injection method which is disclosed in page 4-13 of the Monthly Physics published in Japan [Accelerator Physics (3)].
In the prior art described above, a range of the charged particles which are injected by an injector (in other words, a passing region of the circulating charged particles) at a cross section, which is vertical to the closed orbit, of a vacuum duct wherein the charged particles circulate (the cross section of the vacuum duct means a vertical cross section to the closed orbit if there is no specified comments thereinafter) has been regulated to a linear region from an outlet of the injector to a position in the vacuum duct corresponding to an opposite side of the outlet of the injector with respect to an interval placing the closed orbit at the geometrical center. Therefore, enlargement of the vacuum duct is necessary for increasing the amount of the injected charged particles and increasing of the electric current. The enlargement of the vacuum duct requires enlarging of various electric magnets for circulation of the charged particles and, hence, a problem of enlarging of the whole body of the circular accelerator.
Further, in the prior art described above, an injecting position and an incline of an orbit of the charged particles which are injected from the outlet of the injector into the vacuum duct are necessitated to coincide with the position and the incline of the closed orbit which is set at the outlet of the injector to the circular accelerator. But, the coincidence is difficult because the actual closed orbit of the circular accelerator which is installed differs from the design thereof, and consequently it is impossible to obtain the desired electric current. Accordingly, problems which make the increase of the electric current difficult and, further, a problem that a complex adjustment was necessary for increasing the electric current to the aimed value existed.